In current lighting applications, energy efficiency is a more and more important subject. One possible way to reduce the energy consumption of a lighting system is to switch off or dim one or more light sources thereof when no persons or objects are present in a space, and conversely to switch on the light(s) when a person or an object is present in the space. In order to do this, the presence of a person or object in the relevant space has to be detected. Different types of presence sensors are currently in use.
There is a strong need for sensor-driven light control systems, because of their advantage of bringing down the energy consumption of the light source(s) thereof, and thereby improving cost-savings, and life-time of the light source(s).
Some sensor driven light control systems employ light sensors (e.g., cameras, Position Sensitive Devices (PSD) etc.) that require minimum threshold ambient light levels for accurate sensing. Such light sensors tend to be used because in general they are more accurate than sensors such as passive infrared sensor (PIR) sensors, provided that the minimum threshold ambient light levels are met. However, for some such systems, it is possible that the minimum threshold ambient light levels will not always be met; for example, such systems may drive their respective light source(s) at very low dim levels, or even turned off for energy saving needs, which can lead to ambient light levels which do not meet the required minimum threshold.